perf(spanner): optimize request ID header generation and retry closures - #18408

perf(spanner): optimize request ID header generation and retry closures#18408

olavloite wants to merge 2 commits into

maingoogleapis/google-cloud-python:mainfrom

spanner-optimize-request-idgoogleapis/google-cloud-python:spanner-optimize-request-idCopy head branch name to clipboard